(1) Field of the Invention
The invention relates to thermoelectric energy systems which convert thermal energy into electrical energy. More particularly, the invention relates to a thermoelectric apparatus and a method for converting thermal energy to electrical energy.
(2) Description of the Prior Art
It is known that electrical power can be produced from a thermoelectric cell comprising an electrolyte disposed between two metal electrodes. One type of thermoelectric cell is disclosed in U.S. Pat. No. 3,253,955. This patent discloses an apparatus for obtaining electrical energy from heat energy. One thermoelectric cell disclosed in this patent comprises a container which is divided into chambers or compartments. An ion bridge is positioned between the two chambers and copper electrodes are positioned within each chamber. Each container is filled with an aqueous copper sulfate electrolyte. An aperture is provided between the chambers and an ion bridge is mounted in the aperture. It is stated that the ion bridge can be a sintered glass ion bridge, a porous disc, a salt bridge, an agar-agar salt bridge, an ion permeable membrane, pure difusion (no separation), or other suitable types of bridges known to the art. This patent also states that the cell is reversible, that is, the temperature differential of the cell can be reversed to provide for movement of the copper ions in a reverse direction.
A second type of thermoelectric cell is disclosed in Electrolyte Thermal Piles, Vesz Pren, Hungary (1971), Vol. 1, Hoffman and David. This article discloses a thermoelectric cell comprising an aqueous copper sulfate electrolyte disposed between two metallic copper electrodes. A temperature differential is imposed between the electrodes by heating one electrode and allowing the other electrode to remain at room temperature. A potential difference and a current can be measured between the two copper electrodes. As the temperature differential is applied to the copper electrodes and the cell begins to generate power, the electrodes may become caked or scaled so as to inhibit the further generation of power.
Moreover, a cell of the type disclosed by Hoffmann and David has another drawback. When the temperature difference is applied to the electrodes in the electrolyte, the current output through a constant load decays over a period of time. It is believed that this decay in current output is caused by polarization occurring between the electrodes within the electrolyte and/or by formation of caking or scaling such as oxides or sulfates.
Another type of cell is disclosed in U.S. Pat. No. 2,882,329. This cell comprises two electrodes of the same composition separated by a cation permeable exchange resin membrane which is said to be the sole electrolyte in direct contact with the electrodes. This patent teaches that aqueous electrolytes should not be used in the cell.
It is an object of the present invention to provide a thermoelectric energy system having a relatively high power output.
It is another object of the present invention to provide a thermoelectric energy system which reduces or eliminates corrosion, pitting, scaling or uneven dissolution of electrodes in the system.
It is another object of the present invention to provide a thermoelectric energy system which can be operated without frequent replacement of the electrodes and frequent replenishment of the electrolyte.
It is another object of the present invention to reduce polarization occurring during operation of the thermoelectric energy system.
It is still another object of the present invention to provide a thermoelectric energy system which provides a relatively constant current through a constant load over a relatively long period of time.